docs: def encrypt(self, block):
          """Encrypt blocks."""
  
          if len(block) % 16:
              raise ValueError("block size must be a multiple of 16")
  
          ciphertext = b''
  
          while block:
              a, b, c, d = struct.unpack("<4L", block[0:16])
              temp = [a, b, c, d]
              encrypt(self.context, temp)
              ciphertext += struct.pack("<4L", *temp)
              block = block[16:]
  
          return ciphertext